IGBT with dV/dt Controllability

ABSTRACT

A power semiconductor device includes an active cell region with a drift region of a first conductivity type, a plurality of IGBT cells arranged within the active cell region, each of the IGBT cells includes at least one trench that extends into the drift, an edge termination region surrounding the active cell region, a transition region arranged between the active cell region and the edge termination region, at least some of the IGBT cells are arranged within or extend into the transition region, a barrier region of a second conductivity type, the barrier region is arranged within the active cell region and in contact with at least some of the trenches of the IGBT cells and does not extend into the transition region, and a first load terminal and a second load terminal, the power semiconductor device is configured to conduct a load current along a vertical direction between.

TECHNICAL FIELD

This specification refers to embodiments of a power semiconductordevice, such as an IGBT, and to embodiments of processing a powersemiconductor device. In particular, this specifications refers toembodiments of an IGBT that has a Micro-Pattern-Trench (MPT)configuration, including dummy trenches, wherein a plurality of trenchesextend into an electrically floating barrier region.

BACKGROUND

Many functions of modern devices in automotive, consumer and industrialapplications, such as converting electrical energy and driving anelectric motor or an electric machine, rely on power semiconductordevices. For example, Insulated Gate Bipolar Transistors (IGBTs), MetalOxide Semiconductor Field Effect Transistors (MOSFETs) and diodes, toname a few, have been used for various applications including, but notlimited to switches in power supplies and power converters.

An IGBT usually comprises a semiconductor body configured to conduct aload current along a load current path between two load terminals of theIGBT. Further, the load current path may be controlled by means of aninsulated electrode, sometimes referred to as gate electrode. Forexample, upon receiving a corresponding control signal from, e.g., adriver unit, the control electrode may set the IGBT in one of aconducting state and a blocking state.

In some cases, the gate electrode may be included within a trench of theIGBT, wherein the trench may exhibit, e.g., a stripe configuration or aneedle configuration.

Further, trenches of an IGBT may integrate different types ofelectrodes; some of the electrodes may be connected to the IGBT gateterminal, and others may be connected to an IGBT load terminal, e.g.,the source/emitter terminal.

It is usually desirable to keep losses, e.g., switching losses, of theIGBT low. For example, low switching losses may be achieved by ensuringshort switching durations, e.g., a short turn-on duration and/or a shortturn-off duration.

On the other hand, in a given application, there may also berequirements regarding a maximum slope of the voltage (dV/dt) and/or amaximum slope of the load current (dI/dt).

Further, the switching behavior of an IGBT may depend on its operatingtemperature, wherein it can be desirable to fulfill said provisionsregarding power losses and voltage/current slopes within a broad rangeof possible operating temperatures.

SUMMARY

According to an embodiment, a power semiconductor device comprises anactive cell region with a drift region of a first conductivity type; aplurality of IGBT cells at least partially arranged within the activecell region, wherein each of the IGBT cells comprises at least onetrench that extends into the drift region along a vertical direction; anedge termination region surrounding the active cell region; a transitionregion arranged between the active cell region and the edge terminationregion, the transition region having a width along a lateral directionfrom the active cell region towards the edge termination region, whereinat least some of the IGBT cells are arranged within, or, respectively,extend into the transition region; and an electrically floating barrierregion of a second conductivity type, wherein the electrically floatingbarrier region is arranged within the active cell region and in contactwith at least some of the trenches of the IGBT cells, and wherein theelectrically floating barrier region does not extend into the transitionregion.

According to another embodiment, a power semiconductor device comprisesa first load terminal and a second load terminal, the powersemiconductor device being configured to conduct a load current along avertical direction between said terminals and comprising: an active cellregion with a drift region of a first conductivity type; an edgetermination region having a well region of a second conductivity type; aplurality of IGBT cells arranged within the active cell region, whereineach of the IGBT cells comprises a plurality of trenches that extendinto the drift region along the vertical direction and that laterallyconfine a plurality of mesas. The plurality of trenches include: atleast one control trench having a control electrode; at least one dummytrench having a dummy electrode electrically coupled to the controlelectrode; at least one source trench having a source electrodeelectrically connected with the first load terminal. The plurality ofmesas include at least one active mesa arranged between the at least onecontrol trench and the at least one source trench; and at least oneinactive mesa arranged adjacent to the at least one dummy trench. Thepower semiconductor device further comprises an electrically floatingbarrier region of the second conductivity type, wherein at least both abottom of the dummy trench and a bottom of the source trench extend atleast partially into the electrically floating barrier region, andwherein a portion of the drift region located in a lateral directionbetween the electrically floating barrier region and the well region hasa lateral extension of at least 1 μm in said lateral direction.

According to another embodiment, a power semiconductor device comprisesan active cell region with a drift region of a first conductivity type,a plurality of IGBT cells at least partially arranged within the activecell region, wherein each of the IGBT cells comprises at least onetrench that extends into the drift region along a vertical direction, anedge termination region surrounding the active cell region, a transitionregion arranged between the active cell region and the edge terminationregion, the transition region having a width along a lateral directionfrom the active cell region towards the edge termination region, whereinat least some of the IGBT cells are arranged within, or, respectively,extend into the transition region, a barrier region of a secondconductivity type, wherein the barrier region is arranged within theactive cell region and in contact with at least some of the trenches ofthe IGBT cells, and wherein the barrier region does not extend into thetransition region, and a first load terminal and a second load terminal,the power semiconductor device being configured to conduct a loadcurrent along a vertical direction between the first and second loadterminals, and wherein each IGBT cell has a micro-pattern-trenchstructure.

According to yet another embodiment, a method of processing a powersemiconductor device is presented. The power semiconductor devicecomprises an active cell region with a drift region of a firstconductivity type; a plurality of IGBT cells at least partially arrangedwithin the active cell region, wherein each of the IGBT cells comprisesat least one trench that extends into the drift region along a verticaldirection; an edge termination region surrounding the active cellregion; and a transition region arranged between the active cell regionand the edge termination region, the transition region having a widthalong a lateral direction from the active cell region towards the edgetermination region, wherein at least some of the IGBT cells are arrangedwithin, or, respectively, extend into the transition region. The methodcomprises: providing an electrically floating barrier region of a secondconductivity type, wherein the electrically floating barrier region isarranged within the active cell region and in contact with at least someof the trenches of the IGBT cells, and wherein the electrically floatingbarrier region does not extend into the transition region.

According to another embodiment, a further method of processing a powersemiconductor device is presented. The power semiconductor devicecomprises a first load terminal and a second load terminal, the powersemiconductor device being configured to conduct a load current along avertical direction between said terminals and comprising: an active cellregion with a drift region of a first conductivity type; an edgetermination region having a well region of a second conductivity type; aplurality of IGBT cells arranged within the active cell region, whereineach of the IGBT cells comprises a plurality of trenches that extendinto the drift region along the vertical direction and that laterallyconfine a plurality of mesas. The plurality of trenches include: atleast one control trench having a control electrode; at least one dummytrench having a dummy electrode electrically coupled to the controlelectrode; at least one source trench having a source electrodeelectrically connected with the first load terminal. The plurality ofmesas include at least one active mesa arranged between the at least onecontrol trench and the at least one source trench; and at least oneinactive mesa arranged adjacent to the at least one dummy trench. Thefurther method comprises: providing an electrically floating barrierregion of the second conductivity type, wherein at least both a bottomof the dummy trench and a bottom of the source trench extend at leastpartially into the electrically floating barrier region, and a portionof the drift region located in a lateral direction between theelectrically floating barrier region and the well region has a lateralextension of at least 1 μm in said lateral direction.

In accordance with a yet further embodiment, a power semiconductordevice comprises a first load terminal and a second load terminal. Thepower semiconductor device is configured to conduct a load current alonga vertical direction between said terminals and comprises: a driftregion of a first conductivity type; a plurality of IGBT cells, whereineach of the IGBT cells comprises a plurality of trenches that extendinto the drift region along the vertical direction and that laterallyconfine at least one active mesa, the at least one active mesacomprising an upper section of the drift region; and an electricallyfloating barrier region of a second conductivity type that is spatiallyconfined, in and against the vertical direction, by the drift region.The total volume of all active mesas is divided into a first share andinto a second share, the first share not laterally overlapping with thebarrier region and the second share laterally overlapping with thebarrier region. The first share is configured to carry the load currentat least within the range of 0% to 100% of the nominal load current forwhich the power semiconductor device is designed. The second share isconfigured to carry the load current if it exceeds at least 0.5% of thenominal load current.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The parts in the figures are not necessarily to scale, instead emphasisbeing placed upon illustrating principles of the invention. Moreover, inthe figures, like reference numerals designate corresponding parts. Inthe drawings:

FIG. 1 schematically and exemplarily illustrates a section of ahorizontal projection of a power semiconductor device in accordance withone or more embodiments;

FIGS. 2, 3A, 3B, 4A, and 4B each schematically and exemplarilyillustrates a section of a vertical cross-section of a powersemiconductor device in accordance with one or more embodiments;

FIG. 5 schematically and exemplarily illustrates a course of a dopantconcentration in a power semiconductor device in accordance with one ormore embodiments;

FIGS. 6A-6C schematically and exemplarily illustrate a section of avertical cross-section of a power semiconductor device in accordancewith one or more embodiments;

FIGS. 7 and 8A-8D each schematically and exemplarily illustrate asection of a horizontal projection of a power semiconductor device inaccordance with one or more embodiments;

FIG. 9 schematically and exemplarily illustrate a perspective projectionof a power semiconductor device in accordance with one or moreembodiments;

FIGS. 10-11 each schematically and exemplarily illustrate a section of avertical cross-section of a power semiconductor device in accordancewith one or more embodiments;

FIGS. 12-19 each schematically and exemplarily illustrate a section of ahorizontal projection of a power semiconductor device in accordance withone or more embodiments; and

FIG. 20 schematically and exemplarily illustrates steps of a method ofprocessing a power semiconductor device in accordance with one or moreembodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof and in which are shown byway of illustration specific embodiments in which the invention may bepracticed.

In this regard, directional terminology, such as “top”, “bottom”,“below”, “front”, “behind”, “back”, “leading”, “trailing”, “below”,“above” etc., may be used with reference to the orientation of thefigures being described. Because parts of embodiments can be positionedin a number of different orientations, the directional terminology isused for purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

Reference will now be made in detail to various embodiments, one or moreexamples of which are illustrated in the figures. Each example isprovided by way of explanation, and is not meant as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment can be used on or in conjunction with other embodiments toyield yet a further embodiment. It is intended that the presentinvention includes such modifications and variations. The examples aredescribed using specific language which should not be construed aslimiting the scope of the appended claims. The drawings are not scaledand are for illustrative purposes only. For clarity, the same elementsor manufacturing steps have been designated by the same references inthe different drawings if not stated otherwise.

The term “horizontal” as used in this specification intends to describean orientation substantially parallel to a horizontal surface of asemiconductor substrate or of a semiconductor structure. This can be forinstance the surface of a semiconductor wafer or a die or a chip. Forexample, both the first lateral direction X and the second lateraldirection Y mentioned below can be horizontal directions, wherein thefirst lateral direction X and the second lateral direction Y may beperpendicular to each other.

The term “vertical” as used in this specification intends to describe anorientation which is substantially arranged perpendicular to thehorizontal surface, i.e., parallel to the normal direction of thesurface of the semiconductor wafer/chip/die. For example, the verticaldirection Z mentioned below may be an extension direction that isperpendicular to both the first lateral direction X and the secondlateral direction Y.

In this specification, n-doped is referred to as “first conductivitytype” while p-doped is referred to as “second conductivity type”.Alternatively, opposite doping relations can be employed so that thefirst conductivity type can be p-doped and the second conductivity typecan be n-doped.

In the context of the present specification, the terms “in ohmiccontact”, “in electric contact”, “in ohmic connection”, and“electrically connected” intend to describe that there is a low ohmicelectric connection or low ohmic current path between two regions,sections, zones, portions or parts of a semiconductor device or betweendifferent terminals of one or more devices or between a terminal or ametallization or an electrode and a portion or part of a semiconductordevice. Further, in the context of the present specification, the term“in contact” intends to describe that there is a direct physicalconnection between two elements of the respective semiconductor device;e.g., a transition between two elements being in contact with each othermay not include a further intermediate element or the like.

In addition, in the context of the present specification, the term“electric insulation” is used, if not stated otherwise, in the contextof its general valid understanding and thus intends to describe that twoor more components are positioned separately from each other and thatthere is no ohmic connection connecting those components. However,components being electrically insulated from each other may neverthelessbe coupled to each other, for example mechanically coupled and/orcapacitively coupled and/or inductively coupled. To give an example, twoelectrodes of a capacitor may be electrically insulated from each otherand, at the same time, mechanically and capacitively coupled to eachother, e.g., by means of an insulation, e.g., a dielectric.

Specific embodiments described in this specification pertain to, withoutbeing limited thereto, a semiconductor device, such as an IGBT, e.g.,exhibiting a stripe cell or cellular cell configuration, e.g., an IGBTthat may be used within a power converter or a power supply. Thus, in anembodiment, such IGBT can be configured to carry a load current that isto be fed to a load and/or, respectively, that is provided by a powersource. For example, the IGBT may comprise one or more active powersemiconductor cells, such as a monolithically integrated IGBT cell,and/or a monolithically integrated RC-IGBT cell. Such transistor cellsmay be integrated in a power semiconductor module. A plurality of suchcells may constitute a cell field that is arranged with an active cellregion of the IGBT.

The term “power semiconductor device” as used in this specificationintends to describe a semiconductor device on a single chip with highvoltage blocking and/or high current-carrying capabilities. In otherwords, such power semiconductor device (e.g., an IGBT) is intended forhigh current, typically in the Ampere range, e.g., up to several ten orhundred Ampere, and/or high voltages, typically above 15 V, moretypically 100 V and above, e.g., up to at least 1200 V.

For example, the power semiconductor device described below may be IGBTexhibiting a stripe trench cell configuration or a cellular trench cellconfiguration and can be configured to be employed as a power componentin a low-, medium- and/or high voltage application.

For example, the term “power semiconductor device” as used in thisspecification is not directed to logic semiconductor devices that areused for, e.g., storing data, computing data and/or other types ofsemiconductor based data processing.

FIG. 1 schematically and exemplarily illustrates a section of ahorizontal projection of a power semiconductor device 1 in accordancewith one or more embodiments. FIG. 2 schematically and exemplarilyillustrates a section of a vertical cross-section of a powersemiconductor device 1 in accordance with one or more embodiments. Inthe following, it will be referred to each of FIG. 1 and FIG. 2.

The power semiconductor device 1 can be an IGBT or, respectively, apower semiconductor device that has a configuration that is based on anIGBT configuration, such as Reverse Conducting (RC) IGBT.

For example, the power semiconductor device 1 comprises a semiconductorbody 10 that is coupled to a first load terminal 11 and a second loadterminal 12. For example, the first load terminal 11 is an emitterterminal, whereas the second load terminal 12 can be a collectorterminal.

The semiconductor body 10 may comprise a drift region 100 of the firstconductivity type. The drift region 100 may be n-doped. In anembodiment, the drift region 100 has a (electrically activated) dopantconcentration within the range of 2e12 cm⁻³ to 4e14 cm⁻³. For example,the extension of the drift region 100 along the vertical direction Z andits dopant concentration are chosen in dependence of the blockingvoltage rating for which the power semiconductor device 1 shall bedesigned, as it is known to the skilled person. Within the presentspecification, the term “drift region” is intended to describe suchregion of a power semiconductor device (e.g., an IGBT) the skilledperson typically designates as drift region or, respectively, driftzone.

Further, the first load terminal 11 may be arranged on the frontside ofthe power semiconductor device 1 and may include a frontsidemetallization. The second load terminal 12 may be arranged, opposite tothe frontside, e.g., on a backside of the power semiconductor device 1and may include, for example, a backside metallization. Accordingly, thepower semiconductor device 1 may exhibit a vertical configuration andthe load current may be conducted along the vertical direction Z. Inanother embodiment, each of the first load terminal 11 and the secondload terminal 12 may be arranged on a common side, e.g., both on thefrontside, of the power semiconductor device 1.

Now referring in more detail to FIG. 1, the power semiconductor device 1may further include an active cell region 1-2, an edge terminationregion 1-3 and a chip edge 1-4. The edge termination region 1-3 maysurround the active cell region 1-2. A transition region 1-5 can bearranged between the active cell region 1-2 and the edge terminationregion 1-3. For example, the transition region 1-5 surrounds the activecell region 1-2. The transition region 1-5 can be surrounded by the edgetermination region 1-3.

In an embodiment, the semiconductor body 10 essentially consists of theedge termination region 1-3, the transition region 1-5 and the activecell region 1-2.

For example, each of the edge termination region 1-3, the transitionregion 1-5 and the active cell region 1-2 extend along the verticaldirection Z from the frontside of the power semiconductor device 1entirely through the semiconductor body 10 to the backside of the powersemiconductor device 1. Each of the edge termination region 1-3, thetransition region 1-5 and the active cell region 1-2 may not onlyinclude components of the semiconductor body 10, but also componentsexternal thereof, e.g., components of the first load terminal 11 and/orthe second load terminal 12.

Further, in an example, along lateral directions, there is no overlapbetween the edge termination region 1-3, the transition region 1-5 andthe active cell region 1-2 within the semiconductor body 10. Thus, theactive cell region 1-2 may entirely be surrounded by the transitionregion 1-5, and, within the semiconductor body 10, there is no lateraloverlap, e.g., along the first lateral direction X, the second lateraldirection Y and linear combinations thereof, between the transitionregion 1-5 and the active cell region 1-2. Analogously, the transitionregion 1-5 may entirely be surrounded by the edge termination region1-3, and, within the semiconductor body 10, there is no lateral overlap,e.g., along the first lateral direction X, the second lateral directionY and linear combinations thereof, between the transition region 1-5 andthe edge termination region 1-3.

In an embodiment, the transition region 1-5 has a width W along alateral direction from the active cell region 1-2 towards the edgetermination region 1-3 (e.g., in/against the first lateral direction Xand in/against the second lateral Y and/or in linear combinations of thethese lateral directions) of at least 1 μm. Said width W of thetransition region 1-5 may hence be the distance between the active cellregion 1-2 and the edge termination region 1-3. This (minimum) width Wmay be present along the entire circumference of the transition region1-5. The width of the transition region 1-5 may be greater than 1 μm,e.g., greater than 3 μm, greater than 5 μm or even greater than 10 μm.Further exemplary features of the transition region 1-5 and the edgetermination region 1-5 will be described below. Along said width W, aportion of the drift region 100 may be present.

The chip edge 1-4 may laterally terminate the semiconductor body 10,e.g., the chip edge 1-4 may have become into being by means of waferdicing, for example, and may extend along the vertical direction Z. Theedge termination region 1-3 may be arranged between the active cellregion 1-2 and the chip edge 1-4, as illustrated in FIG. 1.

In the present specification, the terms “active cell region” and “edgetermination region” are employed in a regular manner, i.e., the activecell region 1-2 and the edge termination region 1-3 may be configured toprovide for the principle technical functionalities the skilled persontypically associated therewith.

For example, the active cell region 1-2 of the power semiconductordevice 1 is configured to conduct the main part of the load currentbetween the terminals 11, 12, whereas the edge termination region 1-3does not conduct the load current, but rather fulfills functionsregarding the course of the electric field, ensuring the blockingcapability, safely terminating the active cell region 1-2 and thetransition region 1-5 and so forth, in accordance with an embodiment.

The power semiconductor device 1 comprises a plurality of IGBT cells1-1, wherein the plurality of IGBT cells 1-1 is predominantly arrangedwithin the active cell region 1-2. For example, most of the plurality ofIGBT cells 1-1 of the power semiconductor device 1 are arranged withinthe active cell region 1-2. The number of IGBT cells 1-1 may be greaterthan 100, than 1000, or even greater than 10,000. For example, at least85%, at least 95% or at least 98% of the total number of IGBT cells 1-1are arranged within the active cell region 1-2. In an embodiment, theremaining IGBT cells 1-1 are arranged within the transition region 1-5.Some of the IGBT cells 1-1 may entirely be arranged within thetransition region 1-5, others may be arranged with both within theactive cell region 1-2 and extend, by means of their respective lateralends, into the transition region, as schematically illustrated in FIG.1.

In an embodiment, each IGBT cell 1-1 at least partially extends into thetransition region 1-5, as schematically and exemplarily illustrated inFIG. 1.

Thus, for example, some of the IGBT cells 1-1 are arranged within thetransition region 1-5 or, respectively, extend into the transitionregion 1-5, as schematically and exemplarily illustrated in FIG. 1. Inthis respect, the transition region 1-5 can also be understood as a formof an active region of the power semiconductor device 1. For example, bymeans of said share of the total number of IGBT cells 1-1 that isarranged within the transition region 1-5 or that extends into thetransition region 1-5, the transition region 1-5 may also be configuredto conduct a part of the load current.

In accordance with an embodiment, the IGBT cells 1-1 are not arrangedwithin the edge termination region 1-3. However, within the edgetermination region 1-3, specially configured charge carrier drainagecells (not illustrated in FIG. 1, cf. FIG. 6A-B) may be included thatsupport drainage of charge carriers, e.g., shortly before and/or duringa turn-off operation.

Each IGBT cell 1-1 may exhibit a stripe configuration as schematicallyillustrated in FIG. 1, wherein the total lateral extension in onelateral direction, e.g., along with the second lateral direction Y, ofeach IGBT cell 1-1 and its components may substantially correspond to,or, respectively, slightly exceed the total extension of the active cellregion 1-2 along this lateral direction.

In another embodiment, each IGBT cell 14 may exhibit a cellularconfiguration, wherein the lateral extensions of each IGBT cell 1-1 maybe substantially smaller than the total lateral extensions of the activecell region 1-2.

However, embodiments described herein rather relate to IGBT cells 1-1having a stripe configuration with respect to the second lateraldirection Y, as exemplarily and schematically illustrated in most of thedrawings.

In an embodiment, each of the plurality of IGBT cells 1-1 that areincluded in the active cell region 1-2 exhibit the same set-up. Asection of an exemplary IGBT cell set-up will now be described withrespect to FIG. 2.

The configuration of the IGBT cells 1-1 that may be included within thetransition region 1-5 can be identical to the configuration of the IGBTcells 1-1 that are included in the active cell region 1-2. Additionallyor alternatively, the transition region 1-5 includes IGBT cells thathave a different configuration, e.g., in terms of the MPT contactingscheme/neighborhood relation (cf. more detailed explanations below), ascompared to the IGBT cells 1-1 of the active cell region 1-2.

Each IGBT cell 1-1 comprises at least one trench that extends into thedrift region along the vertical direction Z. Each IGBT cell 1-1 mayextend at least partially into the semiconductor body 10 and comprise atleast a section of the drift region 100. Further, each IGBT cell 1-1 maybe electrically connected with the first load terminal 11. Each IGBTcell 1-1 may be configured to conduct a part of the load current betweensaid terminals 11 and 12, and to block a blocking voltage appliedbetween said terminals 11 and 12.

For controlling the power semiconductor device 1, each IGBT cell 14 maybe equipped with a control electrode 141 included in a control trench 14and configured to selectively set the respective IGBT cell 1-1 into oneof the conducting state and the blocking state.

For example, referring to the example illustrated in FIG. 2, a sourceregion 101 of the first conductivity type may be electrically connectedwith the first load terminal 11. The source region 101 may be n-doped,e.g., at a significantly greater dopant concentration as the driftregion 100.

Further, a channel region 102 of the second conductivity type mayseparate the source region 101 and the drift region 100, e.g., thechannel region 102 can isolate the source region 101 from the driftregion 100, as it is known to skilled person acquainted with generalprinciples of IGBT configurations. The channel region 102 may bep-doped, e.g. with an electrically activated dopant concentration withinthe range of 1e15 cm⁻³ to 5e18 cm⁻³. A transition between the channelregion 102 and the drift region 100 may form a first pn-junction 1021.

For connecting the source regions 101 with the first load terminal 11,first contact plugs 113 can extend from the first load terminal 11 alongthe vertical direction Z so as to contact each of the source region 101and the channel region 102.

The drift region 100 may extend along the vertical direction Z until itinterfaces with a doped contact region 108 that is arranged inelectrical contact with the second load terminal 12. The section of thedrift region 100 arranged between region 105 (explained in more detailbelow) and the doped contact region 108 may form the major part of thedrift region 100. In an embodiment, the dopant concentration of thedrift region 100 increases in the lower section of the drift region 100that forms the interface with the doped contact region 108, e.g., so asto form the field stop region of the first conductivity type, as it isknown to the skilled person.

The doped contact region 108 may be formed in accordance with theconfiguration of the power semiconductor device 1; e.g., the dopedcontact region 108 can be an emitter region of the second conductivitytype, e.g., a p-type emitter. For forming an RC-IGBT, the doped contactregion 108 may be constituted by an emitter region of the secondconductivity type that is interrupted by small sections of the firstconductivity type that are also electrically connected to the secondload terminal 12 and which are commonly referred to as “n-shorts”.

For example, each IGBT cell 1-1 includes at least one control trench 14having said control trench electrode 141 and at least one dummy trench15 having a dummy trench electrode 151, wherein each of said trenches14, 15 may extend into the semiconductor body 10 along the verticaldirection Z and include an insulator 142, 152 that insulates therespective trench electrode 141, 151 from the semiconductor body 10.

The trench electrodes 141, 151 of the at least one control trench 14 andof the at least one dummy trench 15 may each be electrically coupled toa control terminal 13 of the power semiconductor device 1, in accordancewith an embodiment.

Whereas FIG. 2 exemplarily illustrates that the dummy trench 15 isarranged adjacent to the control trench 14, it shall be understood thatthe IGBT cell 1-1 may comprise one or more further trenches of a typedifferent from the control trench type and the dummy trench type, andthat this at least one further trench may be arranged adjacent to thecontrol trench 14. For example, said at least one further trench can bea source trench (reference numeral 16 in other drawings) whose trenchelectrode (reference 161 in other drawings) is electrically connected tothe first load terminal 11. This will be explained in more detail below.

For example, the control terminal 13 is a gate terminal. Further, thecontrol terminal 13 may be electrically connected to the control trenchelectrode 141 and electrically insulated from the first load terminal11, the second load terminal 12 and the semiconductor body 10, e.g., bymeans of at least an insulation structure 132.

In an embodiment, the power semiconductor device 1 may be controlled byapplying a voltage between the first load terminal 11 and the controlterminal 13, e.g., so as to selectively set the power semiconductordevice 1 into one of the conducting state and the blocking state.

For example, the power semiconductor device 1 is configured to becontrolled based on a gate-emitter-voltage V_(GE), e.g., in a principlemanner of controlling an IGBT known to the skilled person.

In an embodiment, the dummy trench electrode 151 may also beelectrically connected to the control terminal 13 and thus receive thesame control signal as the control trench electrode 141. In anotherembodiment, the dummy trench electrode 151 may be electrically coupledto the control terminal 13 by means of a resistor having a resistancewithin the range of 1e⁻³ Ohm to 1 Ohm, within the range of 1 Ohm to 10Ohm, or within the range of 10 Ohm to 100 Ohm. In another embodiment,the dummy trench electrode 151 is electrically connected to a secondcontrol terminal (not illustrated) and thus receives a control signaldifferent from control trench electrode 141.

Further, each IGBT cell 1-1 of the power semiconductor device 1 may haveat least one active mesa 18 electrically connected to the first loadterminal 11, the active mesa 18 comprising the source region 101, thechannel region 102 and a part of the drift region 100, wherein, in theactive mesa 18, respective sections of these regions 101, 102, 100 canbe arranged adjacent to a sidewall 144 of the control trench 14, asexemplarily illustrated in FIG. 2. For example, each of the sourceregion 101 and the channel region 102 are electrically connected to thefirst load terminal 11, e.g., by means of the first contact plug 113.

In an embodiment of the power semiconductor device 1, the doped contactregion 108 is a p-type emitter, and the active mesa 18 may entirelylaterally overlap with the p-type emitter 108.

Further, the control trench electrode 141 (herein also referred to ascontrol electrode 141) can be configured to receive a control signalfrom the control terminal 13 and to control the load current in theactive mesa 18, e.g., by inducing an inversion channel in the channelregion 102 so as to set the power semiconductor device 1 into theconducting state. Thus, a transition 181 between the first load terminal11 and the active mesa 18 may provide for an interface for the loadcurrent to pass from the first load terminal 11 into the semiconductorbody 10 and/or vice versa.

In an embodiment, the inversion channel in the active mesa 18 may beinduced once an inversion channel threshold voltage, e.g., within therespective active mesa 18, is exceeded. For example, the inversionchannel threshold voltage depends on at least one of the work functionof the control electrode 141, the dopant concentration of the sourceregion 101, the dopant concentration of the channel region 102, therelevant thickness of the trench insulator 142, the dielectric constantof the trench insulator 142.

In an embodiment, all active mesas 18 of the power semiconductor device1 are configured with the same inversion channel threshold voltage.

For example, the control electrodes 141 of all IGBT cells 1-1 that areincluded in the active cell region 1-2 may be electrically connected tothe control terminal 13.

In addition to the active mesa 18, each IGBT cell 1-1 of the powersemiconductor device 1 can have at least one inactive mesa 19, e.g.,arranged adjacent to the at least one dummy trench 15, wherein atransition 191 between the first load terminal 11 and the inactive mesa19 provides an electrical insulation at least for charge carriers of thefirst conductivity type.

In an embodiment, the IGBT cell 1-1 may be configured to prevent theload current from crossing said transition 191 between the inactive mesa19 and the first load terminal 11. For example, the inactive mesa 19does not allow for inducing an inversion channel. In contrast to theactive mesa 18, the inactive mesa 19 does not conduct the load currentduring the conducting state of the power semiconductor device 1, inaccordance with an embodiment. For example, the inactive mesa 19 can beconsidered as a decommissioned mesa that is not used for the purpose ofcarrying the load current.

In a first embodiment of the inactive mesa 19, the inactive mesa 19 isnot electrically connected to the first load terminal 11, butelectrically insulated from, e.g., by means of an insulation layer 112.In this embodiment, the transition 191 between the first load terminal11 and the inactive mesa 19 provides an electrical insulation not onlyfor charge carriers of the first conductivity type, but also for chargecarriers of the second conductivity type. To this end, in a variant theinactive mesa 19 comprises neither section of the source region 101 nora section of the channel region 102 nor is the inactive mesa 19contacted by means of a contact plug (cf. reference numeral 111), asillustrated in FIG. 2. In another variant, the inactive mesa 19 may beconfigured in a similar manner as the active mesa 18, e.g., by alsocomprising a section of the source region 101 and/or a section of thechannel region 102, the difference to the active mesa 18 including thatneither the section of the source region 101 (if present) nor thesection of the channel region 102 of the inactive mesa 19 iselectrically connected to the first load terminal 11. In accordance withthe first embodiment of the inactive mesa 19, no current at all crossessaid transition 191.

In a second embodiment of the inactive mesa 19, the inactive mesa 19 maybe electrically connected to the first load terminal 11, wherein thetransition 191 between the first load terminal 11 and the inactive mesa19 provides an electrical insulation only for charge carriers of thefirst conductivity type, but not for charge carrier of the secondconductivity type. In other words, in this second embodiment, theinactive mesa 19 may be configured at allow a current of charge carriersof the second conductivity type, e.g., a hole current, to pass saidtransition 191. For example, depending on the electrical potential ofthe dummy trench electrode 151, such hole current may only temporarilycome into being, e.g., shortly before carrying out a turn-off operation,e.g., so as to reduce the total charge carrier concentration present inthe semiconductor body 10. In an embodiment, this may also occur forsuch inactive mesas 19 with an electrical insulation only for chargecarries of the first conductivity type in a reverse conducting IGBTconfiguration, where the load current would be temporarily carriedthrough these inactive mesas 19 in diode mode operation, where thebackside (cf. doped contact region 108) would be structured to compriseboth emitters of the second conductivity type and emitters of the firstconductivity type (previously referred to as “n-shorts”). As statedabove, in this second embodiment, the inactive mesa 19 may beelectrically connected to the first load terminal 11. For example, adoped contact region (not illustrated) of the second conductivity type(that is different from the electrically floating barrier region 105mentioned below) of the inactive mesa 19 may be electrically connectedto the first load terminal 11, e.g., by means of one of the firstcontact plugs 113, as schematically and exemplarily illustrated in FIG.3B. The doped contact region (not illustrated) of the secondconductivity type may isolate the section of the drift region 100 thatis present within the inactive mesa 19 from the first load terminal 11.For example, in accordance with the second embodiment of the inactivemesa 19, within the inactive mesa 19, there is no region doped withdopants of the first conductivity type that is electrically connected tothe first load terminal 11.

The above illustrated first embodiment and second embodiment of theinactive mesa 19 may allow for providing the configuration of the IGBTcell 1-1 to prevent the load current from crossing said transition 191between the inactive mesa 19 and the first load terminal 11.

The inactive mesa 19 may be laterally confined by the control trench 14and the dummy trench 15, or by the dummy trench 15 and another trenchtype, which will be elucidated further below. Further optional aspectsof the inactive mesa 19 will be described below. For example, eventhough the dummy trench electrode 151 may be electrically connected tothe control terminal 13, in an example, the dummy trench electrode 151is not configured to control the load current in the inactive mesa 19,since the inactive mesa 19 does not allow for inducing an inversionchannel within the inactive mesa 19, in accordance with an embodiment.

The power semiconductor device 1 may further comprise an electricallyfloating barrier region 105 of the second conductivity type (in thefollowing also simply referred to as “barrier region”), as schematicallyexemplarily illustrated in FIG. 2. Exemplary features of this barrierregion 105 will be explained in greater detail further below. Before themore detailed description of the barrier region 105, exemplary aspectsregarding a Micro-Pattern-Trench-Structure (MPT) of the powersemiconductor device 1 shall be explained.

Referring to the embodiments schematically illustrated in FIGS. 3A-B,each IGBT cell 1-1 of the active cell region 1-2 may further comprise atleast one source trench 16 that extends into the semiconductor body 10along the vertical direction Z and includes an insulator 162 thatinsulates a source trench electrode 161 from the semiconductor body 10,the source trench electrode 161 being electrically connected to thefirst load terminal 11. For example, the at least one source trench 16is arranged between the control trench 14 and the dummy trench 15, asillustrated in FIGS. 3A-B. In an embodiment, each IGBT cell 1-1 maycomprise more than one source trench 16, e.g., two source trenches 16(cf. FIG. 4A) or four source trenches 16 (cf. FIG. 6A), wherein each ofthe trench electrodes 161 of the source trenches may be electricallyconnected to the first load terminal 11. For example, the more than onesource trenches 16 are arranged between the control trench 14 on the oneside and the dummy trench 15 on the other side.

In an embodiment, the active mesa 18 may be laterally confined by thecontrol trench 14 and the source trench 16. For example, the sidewall144 of the control trench 14 and a sidewall 164 of the source trench 16confine the active mesa 18 along the first lateral direction X. Theactive mesa 18 may be configured in a manner that has exemplarilydescribed with respect to FIG. 2; e.g., the first contact plug 113 mayelectrically connect each of the section of the channel region 102 andthe section of the source region 101 to the first load terminal 11.

Further, in accordance with the embodiment illustrated in FIGS. 3A-B and4A-B, each IGBT cell 1-1 of the active cell region 1-2 may comprise morethan one inactive mesas 19, wherein at least one of the inactive mesas19 can be laterally confined by the source trench 16 and the dummytrench 15. Another inactive mesa 19 can be laterally confined by twosource trenches 16. Another inactive mesa 19 can be laterally confinedby two dummy trenches 15. Yet another inactive mesa 19 can be laterallyconfined by one of the dummy trenches 15 and the control trench 14. Asillustrated, each of the inactive mesas 19 may comprise a respectivesection of the channel region 102, wherein, in an embodiment, thesesections are not electrically connected to the first load terminal 11but electrically insulated them from, e.g., by means of the insulationlayer 112, as has been explained above.

Referring to the embodiment schematically illustrated in FIGS. 3A-B,each IGBT cell 1-1 of the active cell region may further comprise, inaddition to or as an alternative to the at least one source trench 16,at least one floating trench 17 that extends into the semiconductor body10 along the vertical direction Z and includes an insulator 172 thatinsulates a trench electrode 171 from the semiconductor body 10, thetrench electrode 171 of the floating trench 17 being electricallyfloating. In an embodiment, the trench electrode 171 of the floatingtrench 17 is neither electrically connected to the first load terminal11, nor electrically connected to the second load terminal 12, norelectrically connected to the control terminal 13, nor to a section ofthe semiconductor body 10.

In an embodiment, the electrically floating trench electrode 171 isconnected, by means of a connection having a high ohmic resistance, to adefined electrical potential (e.g., to an electrical potential of acontact or to an electrical potential of another semiconductor region).For example, by means of said high ohmic connection, during a switchingoperation, the electrical potential of the electrically floating trenchelectrode 171 is temporarily decoupled from the defined electricalpotential. Said decoupling may occur on a time scale of said switchingoperation, e.g., for at least 10 ns, or at least 100 ns, or at least 10μs. For example, the resistance of said high ohmic connection amounts tomore than 1e2Ω, or to more than 1 e6Ω. In an embodiment, an ohmicresistance, e.g. measured during a standstill situation, between thefirst load terminal 11 and the electrically floating trench electrode171 amounts to more than 1e2Ω, or to more than 1 e6Ω.

For example, if present, the at least one floating trench 17 can bearranged between the control trench 14 and the dummy trench 15. Further,as illustrated in FIGS. 3A-B, the IGBT cell 1-1 may additionallycomprise said at least one source trench 16, wherein the source trench16 and the floating trench 17 may be arranged between the control trench14 on the one side and the dummy trench 15 on the other side. In anembodiment, the active mesa 18 is laterally confined by the sidewall 144of the control trench 14 and the sidewall 164 of the source trench 16.The inactive mesa 19 may be laterally confined by at least two of thegroup of the sidewall 164 of the source trench 16, the sidewall 174 ofthe floating trench 17, and the sidewall 154 of dummy trench 15.

Thus, in accordance with an embodiment, each IGBT cell 1-1 of the activeregion comprises at least one control trench 14, at least one dummytrench 15, at least one source trench 16 and, optionally, at least onefloating trench 17, wherein the at least one source trench 16 and (ifpresent) the at least one floating trench 17 (if present) can bearranged between the control trench 14 and the dummy trench 15.

In an embodiment, the power semiconductor device 1 can be an IGBT andeach of its IGBT cells 1-1 of its active region 1-2 may exhibit a micropattern trench (MPT) structure.

For example, each or at least most of the trenches 14, 15, 16, 16, 17that may be included in the IGBT cell 1-1 may exhibit equal spatialdimensions and may be arranged in accordance with a regular pattern. Forexample, each of the trenches 14, 15, 16, 16, 17 may exhibit a depthalong the vertical direction Z within the range of 3 μm to 8 μm, and awidth along the first lateral direction X within the range of 0.4 μm to1.6 μm. The trenches 14, 15, 16, 17 can be formed according to a firstlayout having a first pitch, wherein the first layout may define each ofthe trench widths and the mesa widths.

Further, each or at least most of the trench electrodes 141, 151, 161,171 of all trenches 14, 15, 16, 16, 17 that may be included in the IGBTcell 1-1 may exhibit equal spatial dimensions, e.g., regarding the totalextension along the vertical direction (which is terminated by means ofthe respective trench bottoms 145, 155, 165, 175) and the totalextension in the first lateral direction (i.e., the trench width, whichis terminated by means of the respective sidewalls 144, 154, 164, 174),and/or regarding the dimensions of the insulators 142, 152, 162, 172. Inaddition, each of the trenches 14, 15, 16, 16, 17 that may be includedin the IGBT cell 1-1 can be arranged equidistantly along the firstlateral direction X. For example, each of the mesas 18 and 19 of theIGBT cell 1-1 may exhibit the same width, which may be within the rangeof 0.1 μm to 0.3 μm, within the range of 0.3 μm to 0.8 μm, or within therange of 0.8 μm to 1.4 μm.

Further, some of the trenches 14, 15, 16, 16, 17 that may be included inthe IGBT cell 1-1 may extend into the barrier region 105, e.g., by atleast 100 nm, by at least 500 nm or by at least 1000 nm. This aspectwill also be explained in greater detail below.

For the following explanations, these abbreviations may apply:

-   -   G=control trench 14    -   D=dummy trench 15    -   S=source trench 16    -   F=floating trench 17    -   k=active mesa 18    -   o=inactive mesa 19

As has been stated above, the power semiconductor device 1 may comprisea plurality of equally configured IGBT cells 1-1 within the active cellregion 1-2. In an embodiment, using the abbreviations introduced above,an exemplary neighborhood relationship within in each IGBT cell 1-1 ofthe active cell field 1-2 may be expressed as follows:

-   -   oDoSoSkGkSoSoD

Without being limited to this exemplary neighborhood relationship (whichis also being referred to as contacting scheme herein), the embodimentsaccording to most of the remaining drawings are based on the aboveidentified exemplary neighborhood relationship. Thus, it shall beunderstood that the IGBT cells 1-1 must not necessarily comprise afloating trench 17, in accordance with an embodiment.

For example, in another embodiment, each of the IGBT cells 1-1 onlycomprise one or more control trenches 14 and one or more source trenches16. Further, in such embodiment, each of the IGBT cells 1-1 onlycomprises one or more active mesas 18, but no inactive mesas 19. E.g.,the contacting scheme may then be “kGkS” or the like. Then, every trenchelectrode connected to the control terminal 13 would indeed control anactive mesa, e.g., by controlling a respective inversion channel andthere would hence no dummy trenches. In yet another embodiment, the IGBTcells 1-1 only comprise one or more control trenches 14 and one or moreactive mesas, but neither inactive mesas nor a dummy trench, nor asource trench, nor a floating trench.

As indicated above, irrespective of the contacting scheme, the powersemiconductor device 1 may further comprise an electrically floatingbarrier region 105 of the second conductivity type (in the followingalso simply referred to as “barrier region”).

In an embodiment, the barrier region 105 is configured to provide for anelectrically conductive path between a section of the active mesa 18 andthe bottom 155 of the dummy trench 15. Thus, the barrier region 105 maybe configured to guide the electrical potential of the section of theactive mesa 18 to the bottom 155 of the dummy trench 15. For example,the barrier region 105 may extend into the active mesa 18 and from therebelow the bottom 165 of the source trench 16 and across the inactivemesa 19 so as to interface with the bottom 155 of the dummy trench 15.

As has been stated above, the power semiconductor device 1 may comprisea plurality of IGBT cells 1-1, e.g., most of them included in the activecell region 1-2. For example, the barrier region 105 connects theinactive mesas 19 included in the plurality of IGBT cells 1-1 within theactive region 1-2 with each other. For example, to this end, the barrierregion 105 may extend partially into each of the inactive mesas 19. Thebarrier region 105 may further extend, at least partially, into some ofthe active mesas 18. Each of the dummy trench bottoms 155 may extendinto the barrier region 105. Thereby, the barrier region 105 can guidethe electrical potential present within the active mesas towards thedummy trench electrodes 151.

As will be explained in more detail below, the barrier region 105 maylaterally overlap with some (parts) of the active mesas 18 and may notlaterally overlap with other (parts) of the active mesas 18. Forexample, to this end, the barrier region 105 may exhibit a lateralstructure formed by one or more passages 1053, as will be explained inmore detail below, and/or the barrier region 105 may be laterallydisplaced from the edge termination region 1-3 by means of thetransition region 1-5 that may (as explained above) be equipped with oneor more active mesas 18.

Hence, in more general terms, in accordance with an embodiment, a powersemiconductor device 1 is presented that comprises the first loadterminal 11 and the second load terminal 12. The power semiconductordevice 1 is configured to conduct the load current along the verticaldirection Z between said terminals 11,12 and comprises: the drift region100 of the first conductivity type; the plurality of IGBT cells 1-1,wherein each of the IGBT cells 1-1 comprises a plurality of trenches(e.g., 14, 15, 16) that extend into the drift region 100 along thevertical direction Z and that laterally confine the at least one activemesa 18, the at least one active mesa 18 comprising an upper section100-1 of the drift region 100. The electrically floating barrier region105 of the second conductivity type that is spatially confined, in andagainst the vertical direction Z, by the drift region 100.

The total volume of all active mesas 18 can be divided into a firstshare and into a second share, the first share not laterally overlappingwith the barrier region 105 and the second share laterally overlappingwith the barrier region 105. For example, the first share of the activemesas 18 laterally overlaps with the at least one passage 1053 (cf.explanations further below) of the barrier region 105 or with anothersection of the drift region 100 where the barrier region 105 is notpresent (e.g., within the transition region 1-5). In contrast, thesecond share of the active mesas 18 laterally overlaps with the barrierregion 105. For example, the load current conducted by the second sharetraverses the barrier region 105.

In an embodiment, the first share is configured to carry the loadcurrent at least within the range of 0% to 100% of the nominal loadcurrent for which the power semiconductor device is designed. The secondshare may be configured to carry the load current if it exceeds at least0.5% of the nominal load current.

Hence, the first share of active mesas 18 can be considered as an“ignition volume” which, e.g., during turn-on of the power semiconductordevice 1 starts to conduct the load current whereas the second shareinitially remains inactive. Then, if, e.g., only if the load currentexceeds a threshold of, e.g., at least 0.5% of the nominal load current(wherein this threshold can be higher than 0.5%, e.g., higher than 1%,e.g., at least 5% or at least 10%), the barrier region 105 may becomemore conductive such that the second share may also carry the loadcurrent.

For example, for small load currents below 10%, or below 1%, or below0.5% of the nominal load current of the power semiconductor device 1,the active mesas 18 without lateral overlap with barrier region 105(i.e., said first share of the total volume) may act as emitters ofcharge carriers of the first conductivity type, and, e.g., by this avoida snapback in the transfer or output characteristics of the powersemiconductor device 1. For larger load currents (greater than 0.5%,than 1%, than 5% or than 10% of the nominal load current) the upperpn-junction 1051 is in a forward bias mode with respect to the chargecarriers of the first conductivity type. This may then allow also forcharge carriers of the first conductivity type to be emitted by theactive mesas 18 laterally overlapping with the barrier region 105 (i.e.,said second share of the total volume).

As already explained above, each active mesa 18 can be configured toinduce an inversion channel within the respective active mesa 18. Forexample, all active mesas 18 are configured with the same inversionchannel threshold voltage. Thus, the delay between the begin of the loadcurrent conduction within the second volume share and the begin of theload current conduction within the first volume share (according towhich, e.g., during turn-on, the second volume share of the active mesas18 that laterally overlaps with the barrier region 105 only carries theload current once the load current exceeds said threshold value of,e.g., at least 0.5%) exemplarily described above is, e.g., neithercaused by means of providing a control signal to the control electrodescontrolling the first volume share different from a control signalprovided to the control electrodes controlling the second volume share,nor by a difference between inversion channel threshold voltages.Rather, the first volume share and the second volume share are providedwith the same control signal and are configured with the same inversionchannel threshold voltage and said delay is achieved only by accordinglypositioning and/laterally structuring the barrier region 105, inaccordance with an embodiment.

Hence, in an embodiment, the only differentiating feature between thefirst volume share of the active mesas 18 and the second volume share ofthe active mesas 18 is that the first volume share does not laterallyoverlap with the barrier region 105 and that the second volume sharedoes laterally overlap with the barrier region 105. For example,thereby, the said exemplarily described delay between the load currentconduction begins (starting times) is achieved.

For example, once the load current is conducted by both volume shares,it may be distributed among the volume shares in accordance with theratio between the volume shares. In an embodiment, if the load currentexceeds 50% of the nominal load current, the ratio between a first loadcurrent share conducted by the first volume share of the active mesas 18and a second load current share conducted by the second volume share ofthe active mesas 18 can be at least within 10% of the ratio between thefirst volume share and the second volume share or, respectively, theratio between the first load current share conducted by the first volumeshare of the active mesas 18 and the second load current share conductedby the second volume share of the active mesas 18 can be (at leastsubstantially) identical to the ratio between the first volume share andthe second volume share.

The electrically floating barrier region 105 can be spatially confined,in and against the vertical direction Z, by the drift region 100. Hence,the barrier region 105 may form each of an upper pn-junction 1051 and alower pn-junction 1052 with the drift region 100, wherein the lowerpn-junction 1052 can be arranged lower than each of the bottom 155 ofthe dummy trench 15. For example, the upper pn-junction 1051 is arrangedwithin the inactive mesa(s) 19 and, hence, above the bottom 155 of thedummy trench 15. The distance between the first pn-junction 1021 and theupper pn-injunction 1051 along the vertical direction Z may amount to atleast 0.5 μm. Thus, the two pn-junctions 1021 and 1051 are not identicalto each other, but separated from each other by means of the driftregion 100, in accordance with an embodiment.

In other words, the barrier region 105 may be separated from the channelregion 102 by means of at least a part of the drift region 100. Forexample, the barrier region 105 is confined, along the verticaldirection Z, by an upper section 100-1 of the drift region 100 on theone side and by a lower section 100-2 of the drift region 100 on theother side, wherein said upper section 100-1 forms a transition to thechannel regions 102 of the IGBT cells 1-1. The lower section 100-2 mayextend along the vertical direction Z until it interfaces with the dopedcontact region 108, which may be, as illustrated above, a p-typeemitter.

In an embodiment, the barrier region 105 is not in contact with anyother semiconductor region of the second conductivity type, butseparated therefrom, e.g., by means of section(s) of the drift region100. For example, the distance between the barrier region 105 to theclosest other semiconductor region of the second conductivity typeamounts to at least 1 μm or to at least 2 μm. Thus, for example, thereis no p-type connection between the channel regions 102 and the barrierregion 105, nor is there a p-type connection between the barrier region105 and a well region 109 of the edge termination region 109 (mentionedfurther below). Along said distance, a portion of the drift region 100may be present.

With respect to all embodiments discussed above, it shall be understoodthat, in accordance with a variant, the sections of the drift region 100that are included in the mesas 18 and 19, e.g., the upper sections 100-1forming the first pn-junction 1021 with the channel region 102 and theupper pn-junction 1051 with the barrier region 105 (cf. explanationsbelow), may exhibit a dopant concentration at least twice as great ascompared to the dopant concentration of the section of the drift region100 arranged below the barrier region 105, e.g., said lower section100-2 of the drift region 100 that forms the lower pn-junction 1052 withthe barrier region 105.

Said sections (upper sections 100-1) of the drift region 100 that areincluded in the mesas 18 and 19 may each exhibit a maximum dopantconcentration within the range of 1e14 cm⁻³ to 4e17 cm⁻³, e.g., amaximum dopant concentration of at least 1e16 cm⁻³. For example, saidsections of the drift region 100 that are included in the mesas 18 and19 and that may exhibit said increased dopant concentrations can bereferred to as “n-barrier regions”. For example, the dopantconcentration of the sections of the drift region 100 that are includedin the mesas 18 and 19 is chosen such that the upper pn-junction 1051remains at a level slightly above the trench bottoms 145 and 155.

Now referring to FIG. 4B, in accordance with a variant, the increaseddopant concentration in the upper section (section 100-1) of the driftregion 100 is only locally provided. For example, only one of the activemesas 18, or only several of the active mesas 18, or only all of theactive mesas 18 comprise a local n-barrier region 100-3. For example,each of the local n-barrier regions 100-3 is arranged above the barrierregion 105 or, respectively, the barrier region passage 1053, and belowthe respective channel region 102. For example, each n-barrier region100-3 is arranged in contact with the respective channel region 102 andextends from there down along the vertical direction Z until itinterfaces with the (p-) barrier region 105 or, respectively, terminatesat a corresponding Z-level if (p-) barrier 105 is absent/exhibits apassage 1053 at the respective location. Along the first lateraldirection X, each n-barrier region 100-3 may fill the respective activemesa 18. Each n-barrier region 100-3 may exhibit a maximum dopantconcentration at least twice as great as the dopant concentration of thelower section 100-2 of the drift region 100. For example, each n-barrierregion 100-3 exhibits a maximum dopant concentration within the range of1e14 cm⁻³ to 4e17 cm⁻³, e.g., a maximum dopant concentration of at least1e16 cm⁻³. In contrast, in accordance with this variant, the uppersection 100-1 of the drift region included in the inactive mesas 19 mayexhibit a maximum dopant concentration substantially equal to themaximum dopant concentration of the lower section 100-2 of the driftregion 100; e.g., there are no n-barrier regions 100-3 provided withinthe inactive mesas 19.

In a variant (not illustrated), the upper pn-junction 1051 may even bearranged lower than each of the bottom 155 of the dummy trench 15 andsaid bottom 145 of the control trench 14 (wherein this example is notillustrated). In that case, a distance along the vertical direction Zbetween the bottom 155 of the dummy trench 15 and the upper pn-junction1051 can be smaller than 3 μm, smaller than 2 μm, or even smaller than 1μm.

For example, the barrier region 105 exhibits a thickness along thevertical direction Z within the range of 0.1 μm to 0.5 μm, within therange of 0.5 μm to 1 μm, or within the range of 1 μm to 5 μm.

The common vertical extension range along the vertical direction Zbetween the barrier region 105 the trenches that extend into the barrierregion 105 maybe within the range of 50 nm to 3000 nm, for example. Inan embodiment, the barrier region 105 extends further along the verticaldirection Z (i.e., down to a deeper level within the semiconductor body10) as compared to all or, respectively, at least most of the trenches.

The barrier region 105 may exhibit a resistivity of more than 10 Ωcm andof less than 1000 Ωcm, e.g., of more than 100 Ωcm and of less than 500Ωcm, in accordance with an embodiment.

The barrier region 105 may include at least one of boron (B), aluminum(Al), difluoroboryl (BF₂), boron trifluoride (BF₃), or a combinationthereof. A respective one of these exemplary materials may serve as thedopant material, in accordance with an embodiment. Further, a respectiveone of these exemplary materials can be implanted into the semiconductorbody 10 so as to form the barrier region 105.

For example, the barrier region 105 exhibits an electrically activateddopant concentration greater than 1e14 cm⁻³ and smaller than 4e17 cm⁻³.Said dopant concentration, e.g., amounting to approximately 1e16 cm⁻³,may be present with an extension along the vertical direction Z of atleast 0.5 μm, or of at least 1 μm. Further, the barrier region 105 mayexhibit a maximum dopant concentration in a region where the bottom 155of the dummy trench 15 extends into the barrier region 105.

In an embodiment, the dopant concentration of the barrier region 105 issmaller than the dopant concentration present in the channel regions102. For example, the maximal dopant concentration of the barrier region105 is within the range of 1% to 80% of the dopant concentration presentin the channel region 102.

An exemplary course of the dopant concentration (CC) of dopants of thesecond conductivity type along the vertical direction Z is illustratedin FIG. 5, wherein the solid line indicates of dopant concentration thesecond conductivity type (N_(A)) and the dotted line the indicates ofdopant concentration the first conductivity type (N_(D)). Accordingly,in an upper section, e.g., in proximity to the first load terminal 11,the dopant concentration N_(A) may be comparatively high so as toprovide for the channel region 102 (that is not or is not electricallyconnected to the first load terminal in case of the inactive mesa 19,depending on the configuration of the inactive mesa 19, as explainedabove). The dopant concentration N_(A) then decreases rapidly in asection of the mesa where the drift region 100 (said upper section100-1) is present. The transition between the channel region 102 and theupper section 100-1 of the drift region 100 may form said firstpn-junction 1021 within the respective mesa. In case the inactive mesa19 does not comprise a section of the channel region 102, the value ofthe dopant concentration CC between the beginning at the first loadterminal 11 and the beginning of the barrier region 105 wouldaccordingly be at the value corresponding to the local minimum LMillustrated in FIG. 5, or lower. Then, e.g., before the respectivetrench bottom 155, the dopant concentration N_(A) increases (again) soas to form the barrier region 105. The transition with between the uppersection 100-1 of the drift region 100 and the barrier region 105 formsthe upper pn-junction 1051. As illustrated, the barrier region 105 mayexhibit its dopant concentration maximum CCM at the depth level beingsubstantially identical to the level where the respective trenchterminates, e.g., at the level of the bottom 155 of the dummy trench 15.The dopant concentration N_(A) then decreases again so to form the lowerpn-junction 1052 with the lower section 100-2 of the drift region 100.

For example, the electrically floating barrier region 105 is notelectrically connected with a defined electrical potential, e.g.,neither to the first load terminal 11, nor to the second load terminal12, nor to the control terminal 13. In an embodiment, the electricallyfloating barrier region 105 is connected, by means of a connectionhaving a high ohmic resistance, to a defined electrical potential (e.g.,to an electrical potential of a contact or to an electrical potential ofanother semiconductor region). For example, by means of said high ohmicconnection, during a switching operation, the electrical potential ofthe barrier region 105 is temporarily decoupled from the definedelectrical potential. Said decoupling may occur on a time scale of saidswitching operation, e.g., for at least 10 ns, or at least 100 ns, or atleast 10 μs. For example, the resistance of said high ohmic connectionamounts to more than 1e2Ω, or to more than 1e6Ω.

In an embodiment, an ohmic resistance, e.g. measured during a standstillsituation, between the first load terminal 11 and the barrier region 105amounts to more than 1e2Ω, or to more than 1e6 Ω.

For example, for ensuring that the barrier region 105 is electricallyfloating, the barrier region 105 does not extend into the transitionregion 1-5; e.g., the barrier region 105 can exclusively be arrangedwithin the active cell region 1-2, as illustrated in FIG. 1.

For example, the barrier region 105 does not extend into the transitionregion 1-5. As has been explained above, the transition region 1-5 maybe equipped with some of the IGBT cells 1-1 and hence be considered asan active region of the power semiconductor device 1, i.e. a part of thepower semiconductor device 1 that also conducts a part of the loadcurrent.

In an embodiment, the transition region 1-5 does neither include asection of the electrically floating barrier region 105 nor any furtherelectrically floating semiconductor region of the second conductivitytype. For example, there is no floating p-doped semiconductor regionincluded in the transition region 1-5.

The barrier region 105 is electrically floating, and, at the same time,the barrier region 105 can be arranged in contact with at least some ofthe trenches of the IGBT cells 1-1, as has been explained above. Thus,the barrier region 105 may interface with the trench insulators 142, 152and 162. For example, at least the source trench bottom 165 and/or atleast the dummy trench bottom 155 extend into the barrier region 105,e.g., such that the source trench electrode 161, the dummy trenchelectrode 151 and the barrier region 105 have a common verticalextension range along the vertical direction Z of at least 100 nm, of atleast 50 nm or of at least 1000 nm (wherein the barrier region 105 mayextend further along the vertical direction Z as compared to the trenchbottoms).

This aspect shall be elucidated in more detail with respect to FIGS.6A-C, which exemplarily and schematically illustrated a section of avertical cross-section of the power to semiconductor device 1 inaccordance with one or more embodiments, wherein FIG. 6B shows acontinuation from the section of FIG. 6A along the first lateraldirection X, and wherein FIG. 6C shows a continuation from the sectionof FIG. 6B along the first lateral direction X.

Starting at FIG. 6A, the first load terminal 11 may be partially coveredby an insulation structure 80, e.g., an encapsulation. Within the activecell region 1-2, there is arranged a plurality of said IGBT cells 1-1,each of which exhibits said exemplary contacting scheme/neighborhoodrelationship, namely: “oDoSoSkGkSoSoD”. In another embodiment, adifferent contacting scheme is employed.

The active mesas 18 are electrically connected to the first loadterminal 11 by means of said first contact plugs 113, and the sourceelectrodes 161 of the source trenches 16 are electrically connected tothe first load terminal 11 by means of second contact plugs 115. Thecontrol electrodes 141 of the control trenches 14 and the dummyelectrodes 151 of the dummy trenches 15 are electrically connected tothe control terminal 13, e.g., by means of a gate runner 135 (cf. FIG.6B).

Within the transition region 1-5, there is arranged one further IGBTcell 1-1 that may also exhibit the contacting scheme “oDoSoSkGkSoSoD” ora contacting scheme different therefrom. Further along the first lateraldirection X, there is arranged one further dummy trench 15, furthersource trenches 16 and one control trench 14, adjacent to which thereare arranged two active mesas 18. Hence, within the transition region1-5, a part of the load current can be conducted.

The trench pattern may continue along the first lateral direction X alsowithin the edge termination region 1-3, wherein such trenches within theedge termination region 1-3 may be source trenches 16. The mesas betweensaid source trenches 16 may be electrically connected to the first loadterminal 11 by means of the first contact plugs 113. Hence, thearrangement of the source trenches 16 and the mesas in between thesetrenches that are electrically connected to the first load terminal 11may form charge carrier drainage cells.

Within the edge termination region 1-3, there can further be arranged asemiconductor well region 109 of the second conductivity type. Forexample, the well region 109 is p-doped and extends from the insulationlayer 112 along the vertical direction Z, e.g., further as compared tothe total extension of the trenches 14, 15, 16, and 16. For example, thewell region 109 extends about as deep into the semiconductor body as thebarrier region 105.

Still referring to FIG. 6A, the barrier region 105 may terminate at thetransition between the active cell region 1-2 and the transition region1-5. For example, the barrier region 105 is exclusively arranged withinthe active cell region 1-2 and does neither extend into the transitionregion 1-5 nor into the edge termination region 1-3.

On the other side, the well region 109 is exclusively arranged withinthe edge termination region 1-3 and does neither extend into thetransition region 1-5 nor into the active cell region 1-2. As has beenelucidated above, the transition region 1-5 may entirely surround theactive cell region 1-2 and may in turn be entirely surrounded by theedge termination region 1-3. The minimum width W of the transitionregion 1-5, i.e., the minimum distance between the barrier region 105and the well region 109 amounts to 1 μm, wherein said minim width may begreater than 1 μm, e.g. greater than 3 μm, greater than 5 μm or evengreater than 10 μm or than 20 μm. Along said width W, a portion of thedrift region 100 may be present.

As the well region 109 is electrically connected to the first loadterminal 11, e.g., by means of said first contact plugs 113, asexemplarily illustrated, the electrical potential within the well region109 can be substantially identical to the electrical potential of thefirst load terminal 11. Hence, by means of the transition region 1-5 andits minimum width W, it can be more reliably ensured that the barrierregion 105 is indeed electrically floating.

In an embodiment, the well region 109 has an electrically activatedmaximal dopant concentration within the range of 1e1 5 to 5e18 cm⁻³. Itmay extend along the vertical direction Z, e.g., further as the trenches14, 15, 16, e.g. down to a level substantially corresponding to thelower pn-junction 1052 formed between the barrier region 105 and thedrift region 100.

Now referring to FIG. 6B, the well region 109 may extend along the firstlateral direction X until it interfaces with a semiconductor VLD(variation of the lateral doping) or JTE (junction terminationextension) region 107. Also the VLD/JTE region 107 may be of the secondconductivity type and may have a lower dopant concentration than thewell region 109. In general, the concept of such VLD or JTE regionwithin a termination structure of a power semiconductor device is knownto the skilled person and, therefore, it is refrained from explainingthe function of the VLD or JTE region 107 in greater detail herein. Forsafety reasons, the VLD/JTE region 107 may be isolated from theelectrical potential of the gate runner 135 by means of a thicker oxidelayer 85, which may be LOCOS layer or a recessed field oxide.Alternatively, other termination concepts known to the skilled personmay be used.

For example, the gate runner 135 laterally overlaps with each of thewell region 109 and the VLD region 107.

Now referring to FIG. 6C, the VLD region 107 may terminate at theposition within the edge termination region 1-3 well before the chipedge 1-4. The region between the chip edge 1-4 and the termination ofthe VLD region 107 may essentially be constituted by an unstructuredsection of the drift region 100, wherein, in proximity to the chip edge1-4, a channel stopper arrangement can be provided. In general, theconcept of a channel stopper arrangement in proximity to the chip edgeof the power semiconductor device is also known to the skilled person.For example, in accordance with the embodiment exemplarily illustratedin FIGS. 6A-C, for forming the channel stopper arrangement, there isprovided a collector contact 121 that exhibits the electrical potentialof the second load terminal 12. Connected thereto is an electrode of atrench 125. For example, trench 125 follows the course of thetermination region 1-3 in that it also entirely surrounds the transitionregion 1-5. Further trenches 1251 and 1252 may be provided for formingthe channel stopper arrangement. The trenches 125, 1251 and 1252 may beflanked by a semiconductor region 127 of the second conductivity type.

In an embodiment, the barrier region 105 has a lateral structure. Forexample, the barrier region 105 is formed as a laterally structuredlayer that extends throughout the entire active cell region 1-2, e.g.,until it interfaces with the transition region 1-5. Hence, the barrierregion 105 may be exclusively arranged within the active cell region 1-2and does not extend into the transition region 1-5. Within the activecell region 1-2, the barrier region 105 can be laterally structured.

For example, the IGBT cells 1-1 are configured with a lateral structureaccording to a first layout having a first pitch, and wherein thelateral structure of the barrier region 105 is configured according to asecond layout, the second layout having a second pitch at least twice aslarge as the first pitch. Hence, the lateral structure of the barrierregion 105 can be coarser as compared to the trench pattern.

The lateral structure of the barrier region 105 can be formed by aplurality of pass-through passages 1053 (in the following also simplyreferred to as “passages”). Such concept is exemplarily illustrated inthe general manner in FIG. 7. For example, according the second layout,each of the pass-through passages 1053 may exhibit a maximum lateralextension at least twice as large as a minimum trench width and/or aminimum mesa width formed in accordance with the first layout.

In an embodiment, the one or more passages 1053 provide for a loadcurrent passage for currents below 10% or even below 1% of the nominalload current of the power semiconductor device 1. For larger loadcurrents, the whole active cell region 1-2, irrespective of whetherparts bilaterally overlap with the barrier region 105 or not, carry theload current. Thus, in accordance with an embodiment, for load currentsbelow 10% or even below 1% of the nominal load current does not have totraverse the barrier region 105, but may path through the one or morepassages 1053. For example, the barrier region 105 is absent, i.e.,exhibits said passages 1053, in a vertical projection (along thevertical direction Z) of the inversion channels that may be induced inthe active mesas 18, e.g., in a vertical projection of the sourceregions 101.

The possible effect described in the preceding paragraph has also beenelucidated in greater detail above, namely with respect to the firstshare of the total volume of the active mesas 18 that does not laterallyoverlap with the barrier region 105 and the second share of the totalvolume of the active mesas 18 that does laterally overlap with thebarrier region 105.

In an embodiment, the one or more passages 1053 are positioned and/ordimensioned so as to laterally overlap with at least a subset of thesource regions 101.

For example, the barrier region 105 may form a “carpet” arranged withinthe active cell field 1-2 and, e.g., substantially in parallel to eachof the first load terminal 11 and the second load terminal 12 andseparated from each of these terminals 11, 12 by means of at least thedrift region 100. Such carpet like configuration of the barrier region105 may be positioned within the semiconductor body 10 such that thetrench bottoms 145 and 155 and/or 165 may plunge into the barrier region105.

The passages 1053 may laterally overlap with one or more of the activemesas 18. Adhering to the visual vocabulary introduced above, thebarrier region 105 may hence be implemented as a “patchwork carpet”,wherein the one or more passages 1053 can be entirely filled withsections of the drift region 100. The dimensions, the positions and thenumbers of passages 1053 can, for example, be chosen in accordance withthe cell configuration.

The barrier region 105 may be implemented as a contiguous barrier layerwithin the active cell field 1-2 of the power semiconductor device 1,e.g., as said “carpet”. As has been indicated above, each of the dummytrench bottoms 155 and/or the control trench bottoms 145 and or thesource trench bottoms 165 may extend into the barrier region 105, e.g.,the dummy trench 15 and/or the control trench 14 and/or the sourcetrench 16 may extend into the barrier region 105 by at least 100 nm, byat least 500 nm or by at least 1000 nm.

Still referring to FIG. 7, for example, in accordance with variant A,the passages can have a stripe configuration arranged substantiallyperpendicular to the stripe configuration of the IGBT cells 1-1. Inanother embodiment, a central pass-through passage 1053 of largeextensions is provided (variant B). In accordance with variants B and D,a plurality of smaller the passages 1053 is provided, which can bedistributed according to various patterns.

Each of the plurality of passages 1053 can be filled by a section of thedrift region 100. Thus, within the passages 1053, an n-dopedsemiconductor region may be present which exhibits a dopantconcentration corresponding to the dopant concentration of the driftregion. In another embodiment, which will be elucidated in more detailfurther below, some or all of the passages 1053 can also be filled bymeans of (deeper) trenches.

Some embodiments are provided with a barrier region 105 whosepass-through passages 1053 are positioned and dimensioned according to apredefined design rule. For example, said second layout can beconfigured in accordance with the design rule. The positions anddimensions of the passages 1053 may have significant influence on thedynamic behavior of the power semiconductor device 1, e.g., regarding avoltage slope (dV/dt) during a turn-on operation.

For example, in accordance with a first provision of such design rule, adistance between two arbitrary ones of the pass-through passages 1053that are arranged adjacent to each other is smaller than 1 mm.

A second provision of such design rule can be that the barrier region105 is arranged within a semiconductor layer of the semiconductor body10, the semiconductor layer extending entirely and exclusively withinthe active cell region 1-2 and exhibiting a total volume, wherein thepass-through passages 1053 form at least 1% and at most 50% of saidtotal volume. The remaining volume of the semiconductor layer, i.e., thep-doped part of the barrier region 105, can be formed by semiconductorregions of the second conductivity type. As already indicated above,i.e., the remaining volume, can have a dopant concentration (cf.concentration CC in FIG. 5) greater than 1e14 cm⁻³ and smaller than 4e17cm⁻³, said dopant concentration being present within an extension alongthe vertical direction Z of at least 0.1 μm or at least 0.5 μm.

A third provision of such design rule can be, that the barrier region105, despite its passages 1053, connects the inactive mesas 19 includedin the plurality of IGBT cells 1-1 of the active cell region 1-2 witheach other.

A fourth provision of such design rule can be that the passages 1053laterally overlap with at least a subset of the active mesas 18 of theactive cell region 1-2. For example, the one or more passages 1053 arepositioned and/or dimensioned so as to laterally overlap with at least asubset of the source regions 101.

The fifth provision of such design rule can be that the passages 1053laterally overlap with at least a subset of the control trenches 14 ofthe active cell region 1-2.

A further provision of such design rule can be that the barrier region105 extends at least partially into subset of the active mesas 18, e.g.,without establishing contact with the respective control trench 14 thatis laterally flanked by the respective active mesa 18. For example,thereby, the barrier region 105 can be configured to provide for anelectrically conductive path between a section of a respective one ofthe subset of the active mesas 18 and the bottoms 155 of the dummytrenches 15. Hence, it can be provision of the design rule that thepass-through passages 1053 laterally overlap with one or more of theactive mesas 18 of the IGBT cells 1-1. For example, the design rule canspecify that the pass-through passages 1053 laterally overlap, withrespect to the total number of active mesas 18 present within the activecell region 1-2, with at least 1% and at most 50% of the active mesas18. As explained above, the lateral overlap between the barrier region105 and a respective one of the active mesas 18 may occur partially;i.e., the barrier region 105 must not necessarily entirely overlap withthe respective active mesa 18, but, e.g., up to 10%, up to 30% or up to70% of the mesa width of the respective active mesa 18.

With respect to FIGS. 8A-D, which each schematically and exemplarilyillustrate a section of a horizontal projection of a power semiconductordevice 1 in accordance with some embodiments, exemplary lateralstructures of the barrier region 105 shall be presented.

Referring to each of FIGS. 8A-D, the barrier region 105 may extendentirely and exclusively within the active cell region 1-2. Within theactive cell region 1-2, said plurality of IGBT cells 1-1 may beprovided, each of which comprises at least one of said control trenches14 that may be laterally flanked, on each side, by a respective activemesa 18, each of which comprises the source region 101 that iselectrically connected to the first load terminal 11. The IGBT cells 1-1that are included in the active region 1-2 may exhibit a configurationas has been explained with respect to FIGS. 6A-C. The IGBT cells 1-1exhibit a stripe configuration substantially orientated along the secondlateral direction Y, as has also been explained above. For example, eachIGBT cell 1-1 extends along the second lateral direction throughout theentire active cell region 1-2.

In FIGS. 8A-D, a plurality of source regions 101 is illustrated, whereinonly some are provided with a respective reference sign. For example,each of the illustrated source regions 101 forms a part of two activemesas 18, in between which there is arranged a respective control trench14, as illustrated in FIG. 6A.

The active cell region 1-2 can be entirely surrounded by the transitionregion 1-5, which in turn can be entirely surrounded by the edgetermination region 1-3. The transition region 1-5 and the edgetermination region 1-3 may be configured in a manner as has exemplarilybeen explained with respect to FIGS. 6A-C.

As illustrated in FIGS. 8A-D, the lateral structure of the barrierregion 105, which is formed or, respectively defined by the number,dimensions and positions of the passages 1053, can exhibit asignificantly greater pitch as compared to the pitch according to whichthe layout of the trench pattern is formed.

For example, referring to FIG. 8A, the passages 1053 may exhibit anorientation substantially in parallel to the orientation of the stripeconfiguration of the IGBT cells 1-1. A respective one of the passages1053 may laterally overlap with a plurality of adjacent trenches andmesas. It has been pointed out above that it may be appropriate toposition the passages 1053 such that they laterally overlap with atleast a subset of the active mesas 18, which is the case in accordancewith the embodiment illustrated in FIG. 8A; there, the position of thepassages 1053 is chosen such that the passages 1053 overlap with asubset of the source regions 101. Hence, a load current of said subsetof active mesas 18 does not traverse the barrier region 105, but flowsthrough its passages 1053. As further illustrated in FIG. 8A, inaccordance with an embodiment, also the passages 1053 may terminate atthe transition between the active cell region 1-2 and the transitionregion 1-5.

The embodiment illustrated in FIG. 8B essentially corresponds to theembodiment illustrated in FIG. 8A, wherein the passages 1053 aredimensioned and positioned so as to be entirely integrated within thebarrier region 105 and so as to not intersect with the transition region1-5.

In accordance with the embodiment schematically and exemplarilyillustrated in FIG. 8C, the passages 1053 exhibit an orientationsubstantially perpendicular to the orientation of the stripeconfiguration of the IGBT cells 1-1. Such orientation, which is alsoschematically and exemplarily illustrated in the perspective projectionof FIG. 9, may support dampening or, respectively, avoiding of a voltageswing during the switching operation of the power semiconductor device1. The embodiment illustrated in FIG. 8D essentially corresponds to theembodiment illustrated in FIG. 8C, wherein the passages 1053 aredimensioned and positioned so as to be entirely integrated within thebarrier region 105 and so as to not intersect with the transition region1-5.

Now referring to the embodiments that are schematically and exemplarilyillustrated in FIGS. 10 and 11, some or all of the passages 1053 mayalso be filled, in addition or in alternative to the drift region 100,with lower sections of trenches of the IGBT cells 1-1. For example, someor all of the passages 1053 are filled with lower sections of thecontrol trenches 14. In accordance with the embodiment illustrated inFIG. 10, this may be achieved by designing the control trenches 14 was agreater total extension along the vertical direction Z as compared tothe trenches that do not fill the passages 1053. In accordance with theembodiment illustrated in FIG. 11, this may be achieved by providing thebarrier region 105 such that the passages 1053 are arranged withinrespective local elevations (with respect to the vertical direction Z).Further below, exemplary methods of producing structures as illustratedin FIGS. 10 and 11 will be presented.

As further illustrated in FIGS. 10 and 11, in an embodiment, thecontacting scheme is different from the above-mentioned exemplarycontacting scheme, for example, the contacting scheme of each IGBT cell1-1 within the active cell region 1-2 is “oSkGkSoDoD”, but also inaccordance with this contacting scheme, the active mesas 18 arelaterally confined by a respective source trench 16.

Now referring to FIGS. 12 to 19, further exemplary lateral structures ofthe barrier region 105 shall be presented. In accordance with each ofthe embodiments schematically and exemplarily illustrated in FIGS. 12 to19, the contacting scheme for each IGBT cell 1-1 within the activeregion 1-2 is “oDoSoSkGkSoSoD”. However, as noted above, in otherembodiment, a different contacting scheme is employed, examples of whichhave been presented further above.

For example, referring to FIG. 12, the passages 1053 extend in parallelto the stripe configuration of the control trench 14. The barrier region105 partially extends into some of the active mesas 18 that are arrangedadjacent to each side of the respective control trench 14. Asillustrated, the passages 1053 may occur, along the first lateraldirection X, at every fifth IGBT cell 1-1. Hence, a distance D betweentwo neighbored passages 1053 along the first lateral direction X may begreater than 500 μm, e.g., amount to approximately 700 μm. For example,the barrier region 105 hence entirely laterally overlaps with at leastalways exactly 80% of the total number of IGBT cells 1-1 within theactive region 1-2. The remaining 20% of the total number of IGBT cells1-1 within the active region 1-2 may laterally overlap with the passages1053, e.g., by means of their respective control trench 14 and theirrespective active mesas 18, as illustrated in FIG. 12. Further, as alsoillustrated in FIG. 12, the well region 109 does not extend into thetransition 1-5, and the barrier region 105 does also not extend into thetransition region 1-5. Rather, the transition region 1-5 separates thebarrier region 105 from the well region 109.

In accordance with the embodiment shown in FIG. 13, the passages 1053may also each be provided with a smaller rectangular cross-section andpositioned in accordance with an island pattern within the active cellregion 1-2. Each of the passages 1053 may have a width along the firstlateral direction X within the range of 5 μm to 20 μm and the lengthalong the second lateral direction Y within the range of 5 μm to 20 μm.

In an embodiment, for each of the passages 1053, the width along thefirst lateral direction X is greater than the length along the secondlateral direction Y of the respective passages 1053, e.g., thewidth-to-length ratio of each passage is greater than 2, or even greaterthan 3. Hence, the passages may have geometric configuration so as toextend rather perpendicular to the stripe configuration of the IGBTcells 1-1 and not in parallel thereto. Such configuration may bebeneficial for avoiding/reducing an undesired voltage swing/oscillationon the control electrodes 141.

Along the first lateral direction X, each IGBT cell 1-1 (of which, inFIG. 13, only the source regions 101 and the control trenches 14 areillustrated, wherein each of the illustrated source regions 101 iselectrically connected to two respective active mesas 18 that areseparated from each other by means of a respective control trench 14)may laterally overlap with one of the passages 1053. Along the secondlateral direction Y, each IGBT cell 1-1 may laterally overlap with aplurality of the passages 1053. For example, a distance Dx between twopassages 1053 that are neighbored along the first lateral direction X iswithin the range of some micrometers, e.g., 3 μm to 5 μm. Further, adistance Dy between two passages 1053 that are neighbored along thesecond lateral direction Y can be within the range of some micrometers,e.g., 5 μm to 20 μm, e.g. approximately 15 μm.

Along the second lateral direction Y, the source regions 101 can bepositioned with a distance Ds within the range of 0.1 μm to 20 μm. Forexample, each passage 1053 laterally overlaps with at least three of thesource regions 101 along the second lateral direction Y.

A similar configuration is schematically and exemplarily illustrated inFIG. 14. Along the first lateral direction X, each IGBT cell 1-1 maylaterally overlap with one of the passages 1053. Along the secondlateral direction Y, each IGBT cell 1-1 may laterally overlap with aplurality of the passages 1053, wherein the distance Dy along the secondlateral direction is increased as compared to the embodiment shown inFIG. 13.

For example, the passages 1053 do not laterally overlap with the dummytrenches 15. Rather, each of the dummy trenches 15 extends into thebarrier region 105. For example, the passages 1053 overlap partiallywith the control trenches 14 and the source trenches 16.

The lateral structure of the barrier region 105 schematically andexemplarily illustrated in FIG. 15 essentially corresponds to thestructure as illustrated in each of FIGS. 13 and 14. Accordingly, alongthe first lateral direction X, each IGBT cell 1-1 may laterally overlapwith one of the passages 1053. Along the second lateral direction Y,each IGBT cell 1-1 may laterally overlap with a plurality of thepassages 1053, wherein the distance Dy along the second lateraldirection is increased as compared to the embodiment shown in FIG. 14.E.g., the distance Dy between two passages 1053 that are neighboredalong the second lateral direction amounts is within the range ofseveral micrometers, e.g., 1 μm to 2000 μm.

In accordance with variant schematically and exemplarily illustrated inFIG. 16, the lateral structure of the barrier region 105 has achessboard like pattern. According to the embodiment, about 50% of thetotal volume of the barrier region 105 is constituted by the passages1053 (e.g., filled with respective sections of the drift region 100) andthe remaining 50% of the barrier region 105 are p-doped regions. Forexample, each passage 1053 may exhibit a rectangular cross-section. Eachof the passages 1053 may have a width along the first lateral directionX so as to overlap with three neighbored IGBT cells 1-1, and a lengthalong the second lateral direction Y so as to overlap with threeneighbored source regions 101. Along the second lateral direction Y, thesource regions 101 can be positioned within a distance Ds within therange given above. As illustrated, in accordance with the embodiment ofFIG. 16 and in contrast to the embodiment shown in FIG. 14, the passages1053 may laterally overlap with the dummy trenches 15.

In accordance with the further variant that is schematically andexemplarily illustrated in FIG. 17, compared to the lateral structureshown in FIG. 16, the volume share of the passages 1053 may be decreasedfrom 50% to less than 20%. Each of the passages 1053 may have a widthalong the first lateral direction X so as to overlap with threeneighbored IGBT cells 1-1, and a length along the second lateraldirection Y so as to overlap with three neighbored source regions 101.Along the second lateral direction Y, the source regions 101 can bepositioned within a distance Ds within the range given above. Again, asillustrated, also in accordance with the embodiment of FIG. 17 and incontrast to the embodiment shown in FIG. 14, the passages 1053 maylaterally overlap with the dummy trenches 15. Further, the distance thedistance Dx along the first lateral direction X between two neighboredpassages 1053 may amount to the total width of three neighbored IGBTcells 1-1. The distance Dy along the second lateral direction Y may begreater than the distance Dx. For example, the distance Dy along thesecond lateral direction Y between two neighbored passages may amount toat least eight times the distance Ds.

While keeping the dimensions of the passages 1053 unmodified withrespect to the embodiment shown in FIG. 17, in accordance with theembodiment schematically and exemplarily illustrated in FIG. 18, thedensity of the passages 1053 may be increased and, hence, the distancesDx and Dy decreased. As further illustrated in FIGS. 17 and 18, thepassages 1053 may be positioned such that two passages 1053 that areneighbored, at distance Dy, along the second lateral direction Y do notexhibit a lateral overlap along the first lateral direction X (asillustrated in FIG. 17) or such that two passages 1053 that areneighbored, at distance Dx, along the first lateral direction X do notexhibit a lateral overlap along the second lateral direction Y (asillustrated in FIG. 18).

While keeping the dimensions of the passages 1053 unmodified withrespect to the embodiment shown in FIG. 17, in accordance with theembodiment schematically and exemplarily illustrated in FIG. 19, thedensity of the passages 1053 may be decreased and, hence, the distancesDx and Dy increased.

Further variations of the lateral structure of the barrier region 105are possible. For example, each variation of the lateral structure ofthe barrier region 105, e.g., as they are exemplarily and schematicallyillustrated in FIGS. 7 to 19, obeys one or more of the followingprovisions of a design rule:

-   -   (i) a distance, e.g., said distances Dx and Dy, between two        arbitrary ones of the pass-through passages 1053 that are        arranged adjacent to each other is smaller than 1 mm;    -   (ii) the barrier region 105 is arranged within said        semiconductor layer of the semiconductor body 10, the        semiconductor layer extending entirely and exclusively within        the active cell region 1-2 and exhibiting a total volume,        wherein the pass-through passages 1053 form at least 1% and at        most 50% of said total volume. The remaining volume of the        semiconductor layer, i.e., the p-doped part of the barrier        region 105, is formed by semiconductor regions of the second        conductivity type;    -   (iii) the barrier region 105, despite its passages 1053,        connects the inactive mesas 19 included in the plurality of IGBT        cells 1-1 of the active cell region 1-2 with each other;    -   (iv) the passages 1053 laterally overlap with at least a subset        of the active mesas 18 of the active cell region 1-2 (For        example, the one or more passages 1053 are positioned and/or        dimensioned so as to laterally overlap with at least a subset of        the source regions 101);    -   (v) the passages 1053 laterally overlap with at least a subset        of the control trenches 14 of the active cell region 1-2;    -   (vi) the barrier region 105 extends entirely and exclusively        within the active cell region 1-2 (and not into the transition        region 1-5)    -   (vii) the barrier region 105 extends at least partially into        subset of the active mesas 18 (e.g., without establishing        contact with the respective control trench 14 that is laterally        flanked by the respective active mesa 18). For example, thereby,        the barrier region 105 can be configured to provide for an        electrically conductive path between a section of a respective        one of the subset of the active mesas 18 and the bottoms 155 of        the dummy trenches 15.    -   (viii) the lateral structure of the barrier region 105 is        configured according to the second layout that has the second        pitch which is at least twice as large as the first pitch (the        IGBT cells 1-1 are configured with a lateral structure according        to the first layout having the first pitch, as indicated above).    -   (ix) if present (e.g., when the power semiconductor device 1 is        configured as an RC-IGBT), the passages 1053 may laterally        overlap with n-type emitters electrically connected to the        second load terminal 12

As has been explained above, the position and/or the lateral structureof the barrier region 105 (e.g., formed by one or more passages asillustrated in FIGS. 7-19) may allow diving the total volume of theactive mesas 18 into the first share and into the second share, thefirst share not laterally overlapping with the barrier region 105 andthe second share laterally overlapping with the barrier region 105. Asexplained above, the first share of the active mesas 18 laterallyoverlaps with the at least one passage 1053 of the barrier region 105 orwith another section of the drift region 100 where the barrier region105 is not present (e.g., within the transition region 1-5). Incontrast, the second share of the active mesas 18 laterally overlapswith the barrier region 105. For example, the load current conducted bythe second share traverses the barrier region 105. As has further beenexplained above, in an embodiment, the first share is configured tocarry the load current at least within the range of 0% to 100% of thenominal load current for which the power semiconductor device isdesigned. The second share may be configured to carry the load currentonly if it exceeds at least 0.5% of the nominal load current. Hence, thefirst share of active mesas 18 can be considered as an “ignition volume”which, e.g., during turn-on of the power semiconductor device 1 startsto conduct the load current whereas the second share initially remainsinactive. Then, if the load current exceeds the threshold of at least0.5% of the nominal load current (wherein this threshold can be higherthan 0.5%, e.g., higher than 1%, e.g., at least 5% or at least 10%), thebarrier region 105 may become more conductive such that the second sharemay also carry the load current.

Herein presented is also a method of processing a power semiconductordevice. A flow chart of an exemplary method 2 is schematicallyillustrated in FIG. 20. For example, in the first step 2100, asemiconductor body is provided.

The method 2 can be implemented so as to provide a power semiconductordevice that comprises an active cell region with a drift region of thefirst conductivity type; a plurality of IGBT cells at least partiallyarranged within the active cell region, wherein each of the IGBT cellscomprises at least one trench that extends into the drift region along avertical direction; an edge termination region surrounding the activecell region; and a transition region arranged between the active cellregion and the edge termination region, the transition region having awidth along a lateral direction from the active cell region towards theedge termination region, wherein at least some of the IGBT cells arearranged within, or, respectively, extend into the transition region.

For example, method 2 may further comprise step 2200, during which anelectrically floating barrier region of the second conductivity type isprovided, wherein the electrically floating barrier region is arrangedwithin the active cell region and in contact with at least some of thetrenches of the IGBT cells, and wherein the electrically floatingbarrier region does not extend into the transition region.

According to another embodiment, method 2 is implemented so as toprovide a power semiconductor device that comprises a first loadterminal and a second load terminal, the power semiconductor devicebeing configured to conduct a load current along the vertical directionbetween said terminals and comprising: an active cell region with adrift region of the first conductivity type; an edge termination regionhaving a well region of the second conductivity type; a plurality ofIGBT cells arranged within the active cell region, wherein each of theIGBT cells comprises a plurality of trenches that extend into the driftregion along the vertical direction and that laterally confine aplurality of mesas. The plurality of trenches include: at least onecontrol trench having a control electrode; at least one dummy trenchhaving a dummy electrode electrically coupled to the control trench; atleast one source trench having a source electrode electrically connectedwith the first load terminal. The plurality of mesas include at leastone active mesa arranged between the at least one control trench and theat least one source trench; and at least one inactive mesa arrangedadjacent to the at least one dummy trench. Step 2200 may be carried outso as by providing an electrically floating barrier region of the secondconductivity type, wherein at least both a bottom of the dummy trenchand a bottom of the source trench extend at least partially into theelectrically floating barrier region, and wherein a portion of the driftregion located in a lateral direction between the electrically floatingbarrier region and the well region has a lateral extension of at least 1μm in said lateral direction.

For example, regarding both embodiments of method 2 described above, thebarrier region can be formed before forming the trenches of the IGBTcells. In another embodiment, the barrier region is formed after thetrenches of the IGBT cells have been formed. In a yet furtherembodiment, the barrier region is formed during formation of the IGBTcells, e.g. after the trenches have been etched and before the trenchesare filled with trench electrodes.

Exemplary embodiments of the method 2 can correspond to the exemplaryembodiments of the power semiconductor device 1 explained above. Inparticular, method 2 can be carried out so as to form the barrier regionwith a lateral structure, examples of which have been presented above,e.g., with respect to FIGS. 7 to 19.

In an embodiment of method 2, the lateral structure of the barrierregion 105 is formed by creating a homogenously doped p-layer and bylocally providing an n-type counter-doping so as to form the passages1053.

In another embodiment of method 2, the lateral structure of the barrierregion 105 is formed by creating a homogenously doped p-layer andpinching through the layer by means of trench depth variation (cf. FIG.10), e.g., at least partially to a depth beyond the maximum dopantconcentration (cf. CCM in FIG. 5).

In yet another embodiment that the lateral structure of the barrierregion 105 is formed by using a mask arrangement.

For example, the barrier region 105 is fabricated by means of a deepimplantation, e.g., after the formation of the trenches by means ofproviding the trench insulators 142, 152, 162, 172 and the polysiliconfilling for forming the trench electrodes 141, 151, 161, 171. Then,achievement of the projected range (e.g. 5 μm, depending on the trenchdepth, as explained above) of the barrier region 105 could require highimplantation energies, e.g., in the range of 4 MeV, e.g., in case ofboron as the implantation material. For example, masking of theimplantation can be simplified by the presence of a flat surface,following the polysilicon filling of the trenches. The implantation canoccur at high energy, but the dose can be low. Therefore, the trenchinsulators 142, 152, 162, 172 are not damaged.

In an alternative embodiment, the barrier region 105 is created beforethe trench fabrication process. For example, this can be carried out byimplementing a local shallow p-type implantation followed by anepitaxial growth with a target thickness substantially equal to thetrench depth. In this case, slowly diffusing p-type species can beemployed as implantation material. For example, such variant can beemployed for forming the embodiment in accordance with FIG. 10. Thedeeper control trenches 14 can be formed, e.g., by tuning the trenchlayout width and/or by providing separate trench etch blocks for shallowand deeper trenches. Then, the deeper control trenches 14 extend alongthe vertical direction Z beyond the barrier region 105 and enter thedrift region 100, namely its lower section 100-2, as illustrated in FIG.10. With regards to the embodiment illustrated in FIG. 11, the localelevations of the barrier region 105 can be achieved, e.g., by means oflocally providing a counter-doping, e.g., by locally carrying out ann-type implantation. Alternatively, only the p-type implantation iscarried out, wherein, implantation dampening elements may be provided atselected positions on the surface of the semiconductor body 10, e.g., atpositions where one or more of the designated control trenches 14 are tobe formed. Due to the dampening elements, the penetration depth of theimplantation ions is decreased, thereby causing the local elevations inthe barrier region 105 in the outcome. Then, all trenches 14, 15, 16, 17may exhibit the same depth, while those which laterally overlap with thelocal elevations of the barrier region 105 may extend along the verticaldirection Z beyond the barrier region 105 and enter the drift region100, namely its lower section 100-2, as illustrated in FIG. 11. Thereby,the pass-through passages 1053 can be formed, in accordance with anembodiment. For example, the dampening elements are formed by generatinglocal steps on the semiconductor body surface (e.g., by plasma etchingor sacrificial recessed LOCOS), wherein this can be followed by a p-typeimplantation and silicon epitaxial regrowth of proper thickness, so thatthe trenches will align properly to the p-type implantation profile.

In accordance with one or more embodiments described herein, an IGBThaving a plurality of IGBT cells configured in accordance with an MPTstructure is presented, wherein each IGBT cell has a control trench forcontrolling the load current in at least one active mesa and at leastone dummy trench with a trench electrode also electrically connected tothe control terminal and arranged adjacent to the at least one inactivemesa, wherein the active mesa and the bottom of the dummy trench areconnected to each other by means of a laterally structured andelectrically floating p-doped barrier region. Due to such connection,during the switching operation of the IGBT, a voltage swing on thecontrol terminal may be reduced, in accordance with an embodiment. Thismay allow for an improved control of dV/dt by means of a gate signal,e.g., during switching of the IGBT. Furthermore, in an embodiment, thelateral structure of the p-barrier region may avoid a snapback in thetransfer and output characteristics of the IGBT. For example, atcurrents below 10% or even below 1% of nominal load current, the loadcurrent is carried by the active mesas not covered by the p-barrierregion (e.g., where there is barrier passage). For larger currents, anupper pn-junction formed by a transition between the barrier region andthe drift region above the barrier region forward bias mode with respectto the electron current and all active mesas within the active cellregion, irrespective of whether they are covered by a p-barrier regionor not, carry the load current.

In the above, embodiments pertaining to power semiconductor devices andcorresponding processing methods were explained. For example, thesepower semiconductor device are based on silicon (Si). Accordingly, amonocrystalline semiconductor region or layer, e.g., the semiconductorbody 10 and its regions/zones 100, 101, 102, 105, 107, 108, 109 can be amonocrystalline Si-region or Si-layer. In other embodiments,polycrystalline or amorphous silicon may be employed.

It should, however, be understood that the semiconductor body 10 and itsdoped regions/zones can be made of any semiconductor material suitablefor manufacturing a semiconductor device. Examples of such materialsinclude, without being limited thereto, elementary semiconductormaterials such as silicon (Si) or germanium (Ge), group IV compoundsemiconductor materials such as silicon carbide (SiC) or silicongermanium (SiGe), binary, ternary or quaternary III-V semiconductormaterials such as gallium nitride (GaN), gallium arsenide (GaAs),gallium phosphide (GaP), indium phosphide (InP), indium galliumphosphide (InGaPa), aluminum gallium nitride (AlGaN), aluminum indiumnitride (AlInN), indium gallium nitride (InGaN), aluminum gallium indiumnitride (AlGalnN) or indium gallium arsenide phosphide (InGaAsP), andbinary or ternary II-VI semiconductor materials such as cadmiumtelluride (CdTe) and mercury cadmium telluride (HgCdTe) to name few. Theaforementioned semiconductor materials are also referred to as“homojunction semiconductor materials”. When combining two differentsemiconductor materials a heterojunction semiconductor material isformed. Examples of heterojunction semiconductor materials include,without being limited thereto, aluminum gallium nitride (AlGaN)-aluminumgallium indium nitride (AlGalnN), indium gallium nitride(InGaN)-aluminum gallium indium nitride (AlGalnN), indium galliumnitride (InGaN)-gallium nitride (GaN), aluminum gallium nitride(AlGaN)-gallium nitride (GaN), indium gallium nitride (InGaN)-aluminumgallium nitride (AlGaN), silicon-silicon carbide (SixC1-x) andsilicon-SiGe heterojunction semiconductor materials. For powersemiconductor device applications currently mainly Si, SiC, GaAs and GaNmaterials are used.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper” and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the respective device inaddition to different orientations than those depicted in the figures.Further, terms such as “first”, “second”, and the like, are also used todescribe various elements, regions, sections, etc. and are also notintended to be limiting. Like terms refer to like elements throughoutthe description.

As used herein, the terms “having”, “containing”, “including”,“comprising”, “exhibiting” and the like are open ended terms thatindicate the presence of stated elements or features, but do notpreclude additional elements or features.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A power semiconductor device, comprising: anactive cell region with a drift region of a first conductivity type; aplurality of IGBT cells at least partially arranged within the activecell region, wherein each of the IGBT cells comprises at least onetrench that extends into the drift region along a vertical direction; anedge termination region surrounding the active cell region; a transitionregion arranged between the active cell region and the edge terminationregion, the transition region having a width along a lateral directionfrom the active cell region towards the edge termination region, whereinat least some of the IGBT cells are arranged within, or, respectively,extend into the transition region; a barrier region of a secondconductivity type, wherein the barrier region is arranged within theactive cell region and in contact with at least some of the trenches ofthe IGBT cells, and wherein the barrier region does not extend into thetransition region; and a first load terminal and a second load terminal,the power semiconductor device being configured to conduct a loadcurrent along a vertical direction between the first and second loadterminals, and wherein each IGBT cell has a micro-pattern-trenchstructure.
 2. The power semiconductor device of claim 1, wherein thebarrier region forms each of an upper pn-junction and a lowerpn-junction with the drift region, the lower pn-junction being arrangedlower than bottoms of each of the trenches from the plurality of IGBTcells.
 3. The power semiconductor device of claim 1, wherein each IGBTcell comprises: at least one control trench having a control electrode;at least one dummy trench having a dummy electrode; at least one activemesa arranged adjacent to the at least one control trench, wherein thecontrol electrode is configured to receive a control signal from acontrol terminal of the power semiconductor device and to control a loadcurrent in the active mesa; and at least one inactive mesa arrangedadjacent to the at least one dummy trench, wherein a transition betweenthe first load terminal and the inactive mesa provides an electricalinsulation at least for charge carriers of the first conductivity type.4. The power semiconductor device of claim 3, wherein the upperpn-junction is arranged within the at least one active mesa.
 5. Thepower semiconductor device of claim 3, wherein the upper pn-junction isarranged within the at least one inactive mesa, and wherein a transitionbetween the first load terminal and the inactive mesa provides anelectrical insulation at least for charge carriers of the firstconductivity type.
 6. The power semiconductor device of claim 3, whereinthe at least one active mesa comprises a local barrier region of thefirst conductivity type that is arranged above the barrier region andbelow a channel region of the at least one active mesa, the channelregion having the second conductivity type.
 7. The power semiconductordevice of claim 6, wherein a maximum dopant concentration of the localbarrier region is at least twice as great as a maximum dopantconcentration of the drift region.
 8. The power semiconductor device ofclaim 6, wherein: each IGBT cell further comprises at least one sourcetrench having a source trench electrode, the source trench electrodebeing electrically connected to the first load terminal, the at leastone source trench being arranged between the control trench and thedummy trench, or the active mesa being laterally confined by the controltrench and the source trench, or the inactive mesa being laterallyconfined by the source trench and the dummy trench; and each IGBT cellfurther comprising at least one floating trench having a trenchelectrode, the trench electrode of the floating trench beingelectrically floating, the at least one floating trench being arrangedbetween the control trench and the dummy trench, or the at least onesource trench and the at least one floating trench being arrangedbetween the control trench and the dummy trench; and in a verticalcross-section of each IGBT cell, the respective IGBT cell is configuredto prevent the load current from crossing the transition between theinactive mesa and the first load terminal; and each active mesa includesa source region of the first conductivity type that is electricallyconnected to the first load terminal and has a channel region of asecond conductivity type that separates the source region and the driftregion, wherein, in the active mesa, at least a respective section ofeach of the source region, the channel region and the drift region arearranged adjacent to a sidewall of the control trench.
 9. The powersemiconductor device of claim 8, wherein the control electrode and thedummy electrode are each electrically coupled to the control terminal.10. The power semiconductor device of claim 8, wherein the barrierregion is configured to provide for an electrically conductive pathbetween a section of the active mesa and a bottom of the dummy trench.11. The power semiconductor device of claim 8, wherein the barrierregion connects the inactive mesas included in the plurality of IGBTcells of the active cell region with each other.
 12. The powersemiconductor device of claim 11, wherein the barrier region has amaximum dopant concentration in a region where the bottom of the dummytrench extends into the barrier region.
 14. The power semiconductordevice of claim 1, wherein the transition region surrounds the activecell region.
 15. The power semiconductor device of claim 1, wherein thebarrier region is electrically floating.
 16. The power semiconductordevice of claim 1, wherein the barrier region is separated from thechannel region by at least a part of the drift region.
 17. The powersemiconductor device of claim 1, further comprising a floating trenchhaving an electrically floating trench electrode.